I've considered building systems that would speculatively run builds using forward projections of all pending pull requests, as well as run multiple parallel scenarios on merge order + rebase such that merge conflicts are minimized. Maybe sprinkle in some monte carlo if the numbers get a little intense.

In practice, I feel it is much easier to assign work and organize your codebase so that logically-different business functions can be managed in isolation.

We rarely have merge conflicts these days, and we are also on 1 big monorepo. It mostly boils down to discipline and architecture.